The present invention relates to a process and an apparatus for preparing bias-cut cord fabric used as ply stock in the manufacture of pneumatic tires.
In the conventional factory process a wide sheet of tire cord fabric is passed between calender rolls and coated with unvulcanized rubber. This sheet of rubberized fabric is fed by a first cutter conveyor to an adjustable bias cutter wherein lengths of the material are cut at a bias angle to form panels of parallelogram shape, the width of the cut panels corresponding to the width of a tire ply. These bias-cut panels are then transferred manually or mechanically from the cutter to a takeaway conveyor and spliced together at their uncut side portions to form a continuous strip of ply stock with the cords extending from one side of the strip to the other. The continuous length of ply stock is stored on a supply roll and later cut or separated into individual plies at the tire building drum.
The cutting is carried out using conventional adjustable bias cutters which may, for example, be of the type disclosed in U.S. Pat. Nos. 2,962,083; 3,757,618 and 4,069,729.
The splicing may be carried out manually but is preferably performed in a lap splicer or a butt splicer which may be adjusted to accommodate fabric panels of many different sizes and bias angles. The splicer may, for example, be of the type disclosed in any one of U.S. Pat. Nos. 3,100,731; 3,130,100; 3,325,328; 3,355,343; and 3,433,690.
In the tire factory, the bias-cut panels are transferred from the cutter conveyor and/or the bias cutter to a second conveyor leading to the splicer (see U.S. Pat. Nos. 2,754,953 and 2,962,083). Such transfer can be effected manually or by use of automatic transfer means. Such means may, for example, be of the general type disclosed in U.S. Pat. Nos. 2,962,083; 3,019,018; 3,037,548; 3,077,803; and 4,087,308.
Because of the size of the bias-cut panels, the need to position the panels accurately for splicing, and other reasons, a substantial amount of time is usually required to carry out the transfer in a satisfactory manner. Automatic equipment for effecting such a transfer has heretofore been complicated and expensive because of the requirement of precision in positioning the transferred panels and the need to accommodate changes in the bias angle as well as changes in the length and width of the panels being spliced. Maintaining a reasonable rate of production is difficult with such transfer devices, and serious problems arise as the size of the cut panels is increased. When producing carcass ply stock with a width up to 4 ft., the maximum rate of factory production is about 10 to 12 panels per min. At higher speeds, maintenance problems become severe and the equipment cannot perform with the necessary degree of precision and reliability.
Problems become more severe as the size of the cut panels is increased. Generally the automatic transfer equipment is unsatisfactory when producing ply stock with a width substantially greater than 4 ft for large truck tires or off-the-road (OTR) tires. For this reason tire factories have continued to rely on manual transfer and manual splicing of bias-cut panels when producing OTR carcass ply stocks.